Semiconductor memory is an important part of modern electronics. Like other silicon technology, memory has been growing in density and performance. This growth in density and performance has so far generally followed Moore's law, i.e., the number of transistors that can be placed inexpensively on an integrated circuit has doubled approximately every two years. The increase in signaling speed of memory interfaces are also strongly linked to Moore's law.
The signaling speed of memory interfaces is limited by the speed at which a given communication channel can transition between different signaling levels, which are used to communicate different symbols. The time required to transition between symbols can vary with symbol patterns, making it difficult to identify symbol boundaries at high data rates. As the symbol boundaries become less clear, inter-symbol-interference becomes a major issue in high-speed memory systems.